Akt and CHIP coregulate tau degradation through coordinated interactions

Chad A. Dickey, John Koren, Yong Jie Zhang, Ya Fei Xu, Umesh K. Jinwal, Morris J. Birnbaum, Bobby Monks, Mei Sun, Jin Q. Cheng, Cam Patterson, Rachel M. Bailey, Judith Dunmore, Sareh Soresh, Carlos Leon, Dave Morgan, Leonard Petrucelli

Research output: Contribution to journalArticlepeer-review

146 Scopus citations

Abstract

A hallmark of the pathology of Alzheimer's disease is the accumulation of the microtubule-associated protein tau into fibrillar aggregates. Recent studies suggest that they accumulate because cytosolic chaperones fail to clear abnormally phosphorylated tau, preserving a pool of toxic tau intermediates within the neuron. We describe a mechanism for tau clearance involving a major cellular kinase, Akt. During stress, Akt is ubiquitinated and degraded by the tau ubiquitin ligase CHIP, and this largely depends on the Hsp90 complex. Akt also prevents CHIP-induced tau ubiquitination and its subsequent degradation, either by regulating the Hsp90/CHIP complex directly or by competing as a client protein with tau for binding. Akt levels tightly regulate the expression of CHIP, such that, as Akt levels are suppressed, CHIP levels also decrease, suggesting a potential stress response feedback mechanism between ligase and kinase activity. We also show that Akt and the microtubule affinity-regulating kinase 2 (PAR1/MARK2), a known tau kinase, interact directly. Akt enhances the activity of PAR1 to promote tau hyperphosphorylation at S262/S356, a tau species that is not recognized by the CHIP/Hsp90 complex. Moreover, Akt1 knockout mice have reduced levels of tau phosphorylated at PAR1/MARK2 consensus sites. Hence, Akt serves as a major regulator of tau biology by manipulating both tau kinases and protein quality control, providing a link to several common pathways that have demonstrated dysfunction in Alzheimer's disease.

Original languageEnglish (US)
Pages (from-to)3622-3627
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number9
DOIs
StatePublished - Mar 4 2008

Keywords

  • Alzheimer's disease
  • Cell signaling
  • Chaperone
  • MARK2/PAR1

ASJC Scopus subject areas

  • General

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